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A dead ant killed by a microbial parasite known as the "zombie ant" fungus clings to the underside of a twig, where the fungal fruiting body growing from the ant's head will shoot spores to infect more ants below.

Image: Hughes Lab, Penn State

Researchers to study how microbes become 'fungi in ant's clothing'

Chuck Gill

June 8, 2016

Researchers to study how microbes become 'fungi in ant's clothing'

UNIVERSITY PARK, Pa. — A pair of grants worth more than $2 million will enable Penn State researchers to study how microbial parasites control the behaviors and characteristics of their animal hosts.

The National Institutes of Health recently awarded $1.6 million to a research team led by David Hughes, assistant professor of entomology and biology, to study microbes in the genus Ophiocordyceps -- known as "zombie-ant" fungi -- and how they behave "from cells to societies."

"Microbes can be social," said Hughes, who has appointments in the College of Agricultural Sciences and the Eberly College of Science. "In some groups of microbes that have parasitic lifecycles, the social behavior of the many microbial cells can lead to the precise control of the animal they infect. The microbes orchestrate within the body to form interactions that are as impressive as any other collective behavior, from shoals of fish and flocks of birds to ant trails."

Hughes' lab studies how zombie-ant fungi precisely control ants, compelling them to leave their nest and bite into vegetation directly over the foraging trails of the colony, where they die. The fungi then grow a stalk from the ant's head that shoots out spores to infect other ants below.

The goal of the NIH project is to develop models of such complex collective behavior by fungi. The research team will develop computational and physical diffusion models of the development of the fungal collective within its ant host. Using high-throughput scanning electron microscopy of ant muscles and computer vision algorithms, the scientists will develop 3-D computational models and accurate networks of cells.

"We will perform micro-acoustic fluidic experiments to measure fungal behavior and develop physical diffusion models of the emergence of collective behavior," Hughes said. "At the macroscopic scale, we'll measure infected ant behavior in the forest and build agent-based models to determine the rules explaining the effective targeting of ant trails by the fungal collective using the ant as a vehicle. Finally, we will perform experiments to understand the role of competition in the social behavior of microbes."

Other researchers on the project are Ephraim Hanks, assistant professor of statistics, Eberly College of Science; Francesco Costanzo, professor of engineering science and mechanics and mathematics, Penn State College of Engineering; and Danny Chen, professor of applied computational mathematics and statistics, University of Notre Dame.

In a separate project, funded by a grant of approximately $560,000 from the National Science Foundation, a team led by Hughes will study the biochemical mechanisms behind the complex manipulation of the ant host by the fungi. Employing transcriptomics, metabolomics and histology, the researchers will ask how, across the three-week period of infection, the fungi within the body effectively take control of the ant.

"This manipulation is all the more spectacular for the fact that the organism without the brain controls the one with the brain," Hughes said. "In this project, we will use an integrative approach to ask how fungi change ants from productive members of their colony to 'fungi in ant's clothing.'"

He noted this work will provide insights into the nature of parasitism and ultimately may be of broader societal relevance because the fungi his lab studies are known to be important sources of small molecules with medical relevance.

The research team also includes Andrew Patterson, associate professor of molecular toxicology in the College of Agricultural Sciences; Philip Smith, senior research associate and director of the Metabolomics Core Facility in the Huck Institutes of the Life Sciences; and Greg Ning, director of the Huck Institutes' Microscopy and Cytometry Facility.

Hughes credited the collaborative research environment at Penn State for making projects such as these possible.

"Most of our collaborators on these grants are part of different academic colleges but are housed in the Huck Institutes of the Life Sciences," he said. "This proximity and regular interaction fosters creativity and research opportunities that cross disciplines and academic units, and I'm aware of few other universities where these types of collaborations are so prevalent."